Safety system for a gas fueled water heater

ABSTRACT

A system for monitoring temperature in the combustion chamber of a gas fueled water heater using a thermoelectric device placed near the gas burner. Based on the measured temperature, the water heater can determine whether abnormal operation is occurring that would require closing the flow of gaseous fuel to e.g., the main burner, pilot burner, or both.

FIELD OF THE INVENTION

The subject matter of the present disclosure relates generally to temperature monitoring and gas flow control in the combustion chamber of a gas water heater.

BACKGROUND OF THE INVENTION

A variety of energy sources are used in creating hot water for commercial and residential use including electric, solar, and various fuels. Natural gas and propane are preferred by some customers due to e.g., the relatively quick heating rate. These fuels are supplied as a gas that is burned in a combustion chamber to provide heat energy to raise the water temperature.

Temperatures in the combustion chamber are relatively high and can e.g., reach 600 degrees Fahrenheit of higher during normal operation. A flame is created by burning a mixture of the gaseous fuel and air. Proper combustion requires that the air and fuel are provided within a particular ratio to ensure e.g., complete combustion and avoid wasted fuel or the production of unwanted by-products such as carbon monoxide.

If the water heater is e.g., installed in a dusty area containing above average levels of e.g., dirt, oil, or lint, the air intake of water heater can become clogged. The lack of enough air can cause the temperature of the combustion chamber to become too hot. As another example, a flammable vapor event such as a the ignition of vapor from liquid fuel present near the water heater can also create elevated temperatures in the water heater combustion chamber.

Accordingly, it is desirable to monitor temperature and terminate the combustion process by e.g., shutting off the gas flow if the temperature reaches unsafe levels.

One conventional approach is the use of a bi-metal switch placed in direct contact with the wall of the combustion chamber so as to activate the switch. The metals of the bi-metal switch have different thermal expansion characteristics. Once the temperature of the bi-metal switch reaches a predetermined maximum temperature, the switch is activated so as to cause a control system to close off the flow of gas—even if the temperature is only high for a relatively short period of time. Then, the bi-metal switch must cool before allowing the water heater to operate again or, alternatively, the bi-metal switch must be manually reset. Such reset requirement can be undesirable, particularly if the increased temperature was not due to a unwanted event such as clogging of the air flow.

Also, because the bi-metal switch must be placed in contact with the combustion chamber wall, it does not provide a direct measurement of the temperature of the combustion process. Instead, heat must be transmitted to the wall of the combustion chamber before the bi-metal switch can be triggered due to an unsafe condition. Furthermore, the bi-metal switch does not provide for multiple temperature measurements or adjustment of the temperature at which it is activated. Instead, the bi-metal switch is simply activated upon reaching a predetermined maximum temperature.

Accordingly, an improved system for measuring and monitoring the temperature of the combustion chamber of a gas water heater is needed.

BRIEF DESCRIPTION OF THE INVENTION

The present invention provides a system for monitoring temperature in the combustion chamber of a gas fueled water heater using a thermoelectric device placed near the gas burner. Based on the measured temperature, the water heater can determine whether abnormal operation is occurring that would require closing the flow of gaseous fuel to e.g., the main burner, pilot burner, or both. Additional aspects and advantages of the invention will be set forth in part in the following description, or may be apparent from the description, or may be learned through practice of the invention.

In one exemplary embodiment, the present invention provides a gas fueled water heater that includes a tank for storage of water for heating, a combustion chamber, and a gas burner positioned adjacent to the tank and within the combustion chamber, the gas burner configured for heating the water in the tank. A valve provides for controlling a flow of gaseous fuel to the gas burner. A thermopile is positioned within the combustion chamber near the gas burner. The thermopile is configured to provide a signal representing temperature, TP, as measured in the combustion chamber. A controller is configured for receiving the signal from the thermopile and for terminating a flow of gaseous fuel to the gas burner if the temperature TP is the same or greater than a predetermined maximum temperature, TP_(MAX).

In another exemplary aspect, the present invention provides a method of operating a gas fueled water heater. The water heater has a combustion chamber and a thermopile for measuring temperature in the combustion chamber. The method includes generating a signal representing the temperature, TP, in the combustion chamber as measured by the thermopile; and determining whether the temperature TP is the same or greater than a predetermined temperature TP_(MAX) If temperature TP is the same or greater than a predetermined temperature TP_(MAX), then this exemplary method includes terminating a flow gaseous fuel to a gas burner located in the combustion chamber.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:

FIG. 1 provides a partially cut away, side view of an exemplary embodiment of a water heater of the present invention.

FIG. 2 provides a perspective view of an exemplary gas combustion chamber as may be used with the exemplary water heater of FIG. 1.

FIG. 3 provides a close-up view of certain exemplary components positioned adjacent to burner of the exemplary water heater of FIGS. 1 and 2.

FIG. 4 is a schematic of a gas flow control system as may be used with the exemplary water heater of FIG. 1.

FIG. 5 is an exemplary, representative plot of temperature measurements as further described herein.

FIG. 6 provides a flowchart illustrating an exemplary method of operation of the exemplary water heater in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

FIG. 1 illustrates a partial sectional, side view of an exemplary water heater 100 of the present invention. Water heater 100 includes a tank 102 where water is stored and heated. Water is supplied to tank 102 by inlet line 104. Heated water is supplied by tank 102 through outlet line 106. Water heater 100 is fluidly connected with lines 104 and 106 using connections 132 and 134. In turn, lines 104 and 106 connect with the water supply system of e.g., a residence or a commercial structure.

From line 104, water travels into tank 102 through a cold water dip tube 122 that extends along vertical direction V towards the bottom 114 of tank 102. After being heated, water exits tank 102 by travelling vertically upward and out through outlet line 106. Anode rod 126 provides protection against corrosion attacks on tank 102 and other metal components of water heater 100. A pressure relief valve 128 provides for a release of water from tank 102 in the event the pressure rises above a predetermined amount.

Water heater 100 includes a combustion chamber 110 in which a gas burner 108 is centrally located. Gas burner 108 is supplied with a gaseous fuel e.g., propane or natural gas. Air travels into combustion chamber 110 through air intake 112 in cabinet 130. The resulting mixture of air and gas is ignited and burned to heat bottom 114 of tank 102 and its water contents. Hot combustion gas 120 exits combustion chamber 110 through a vent or flue 124 centrally located within tank 102. Heat exchange with flue 124 also helps heat water in tank 102. A baffle 120 promotes this heat exchange. Gas 120 exits water heater 100 though vent hood 136, which may be connected with additional vent piping (not shown).

A thermostat 116 measures the temperature of water in tank 102 and provides a signal to gas control valve module 118. As used herein, “a signal” is not limited to a single measurement of temperature and, instead, may include multiple measurements over time or continuous measurements over time. The signal may be provided through e.g., changes in current, voltage, resistance, or others. Depending upon whether the desired temperature has been reached as determined e.g., from the signal from thermostat 116, gas control valve module 118 regulates the flow of gas to burner 108.

Referring now to FIG. 2, combustion chamber 110 is formed by a chamber wall 138 that at least partially encloses combustion chamber 110 and may also provide support for tank 102 along top edge 160. As shown, chamber wall 138 encircles burner 108 and is spaced apart from burner 108. Chamber wall 138 may be part of cabinet 130 (FIG. 1) or may be a separate component.

FIG. 3 provides a close-up view of certain components positioned beneath and directly adjacent to gas burner 108. FIG. 4 provides a schematic representation of combustion chamber 110 and certain other components as will be further described. As shown, water heater 102 includes a pilot burner 148 that provides a pilot light 150 (FIG. 4) to ignite a mixture of air and fuel at burner 108 when a gas valve 146 is open. An igniter 158 is positioned adjacent to pilot burner 148 and generates a spark used to ignite gaseous fuel and provide pilot light 160. Gaseous fuel for pilot burner 108 is supplied by pilot burner fuel line 152. Gas valve control module 118 with controller 154 controls the flow of gaseous fuel through pilot burner fuel line 152 and the flow of gas to burner 108 from gaseous fuel supply 168.

A thermopile 156 is positioned adjacent to the pilot burner 148 and igniter 158. Thermopile 156 can convert heat from pilot burner 148 into electrical energy, which can be used e.g., to power gas valve control module 118. Thermopile 156 also provides a voltage signal representing temperature TP as measured by thermopile 156 in combustion chamber 110. Thermopile 156 may be constructed from e.g., a plurality of thermocouples connected in a series, for example. The output voltage from thermopile 156 is proportional to the temperature. Thermopile 156 provides a voltage signal to controller 154 through conductors 164 representing the measured temperature TP. For this exemplary embodiment, a bracket 166 is used to position pilot burner 148, igniter 158, and thermopile 156 near gas burner 108. Thermopile 156 is provided by way of example. Other thermoelectric devices providing a voltage signal proportional to the temperature and capable of powering gas control valve module 118 may be used as well.

Gas valve control module 118 includes at least one controller 154. By way of example, controller 154 may include memory and one or more processing devices such as microprocessors, CPUs or the like, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with operation of water heater 100 as further described herein. The memory can represent random access memory such as DRAM, or read only memory such as ROM or FLASH. The processor executes programming instructions stored in the memory. The memory can be a separate component from the processor or can be included onboard within the processor. Alternatively, controller 154 may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.

As stated, water heater 100 includes a gas valve 146 positioned along main gas supply line 168. Controller 154 is in communication with gas valve 146 to control the flow of gas therethrough by determining when valve 146 is energized. For this exemplary embodiment, gas valve 146 operates so that when energized, valve 146 is fully open to allow a flow of gaseous fuel to burner 108. When not fully energized, valve 146 is fully closed (i.e. a “fail-closed” type valve) so as to prevent the flow of gaseous fuel to burner 108.

FIG. 5 provides an exemplary plot of temperature signals from thermopile 156 representing temperature TP as measured in combustion chamber 110 under various conditions. For example, temperature curve 200 represents the temperature TP measured before, during, and after ignition of gaseous fuel to create a pilot light 150 at pilot burner 148 but without a flame at burner 108. As shown, once pilot burner 148 reaches steady state conditions in combustion chamber 110, thermopile 156 provides a relatively constant signal to controller 154 representing the temperature, T_(PPILOT) at which pilot light 150 is present. For this particular example, the temperature measured near pilot 150 is around 490° F. However, other predetermined temperatures can be used for T_(PPILOT) including 490° F., 500° F., 510° F., and others.

Upon receiving a signal from thermopile 156 indicating TP_(PILOT) has been reached or exceeded, gas control module 118 can continue to allow the flow of gas to pilot burner 148. If the temperature signal TP indicates the temperature is below TP_(PILOT), thereby indicating that pilot light 150 is not present, then controller 154 of gas control module 118 can terminate the flow of gaseous fuel along line 152 to pilot burner 148. In such case, a user must manually override controller 154 to provide gaseous fuel to pilot burner 148 while causing igniter 158 to spark so as to create pilot light 150. Once the condition of TP≥TP_(PILOT) is met, then controller 154 can allow a continuous flow of gaseous fuel to pilot burner 148.

Temperature curve 202 represents temperature TP measured by thermopile 156 before, during, and after ignition of gaseous fuel to create a flame 162 at burner 108. Once steady state conditions are reached in combustion chamber 110, thermopile 156 provides a relatively constant signal to controller 154 representing the temperature, TP_(BURN), at which a flame 162 is present at burner 108. For this particular example, TP_(BURN) is about 1050° F. However, other temperatures can be used for TP_(BURN) including e.g., 1100° F. By way of example, controller 154 can use a signal from thermostat 116 to determine whether the temperature of water in tank 102 has reached a desired setpoint temperature. If so, then controller 154 can terminate the flow of gaseous fuel to burner 108 from gas supply 168 by causing valve 146 to close. If the temperature of water in tank 102 has not reached the desired setpoint temperature, controller 154 can allow valve 146 to remain open until temperature TP as reported using a signal from thermopile 156 is at or about TP_(PILOT).

Temperature curve 204 represents temperature TP measured in combustion chamber 110 by thermopile 156 before, during, and after ignition of gaseous fuel to create a flame 162 at burner 108. However, unlike temperature curve 202, temperature curve 204 indicates that an abnormal condition has occurred in combustion chamber 110. More particularly, at approximately 200 seconds in this example, the temperature in combustion chamber 110 reaches 1200° F. and continues to climb. As previously described, for various reasons, the combustion of gaseous fuel in combustion chamber 110 may be incomplete—potentially creating carbon monoxide and undesirable, elevated temperatures. For example, air intake 112 may be clogged or blocked such that the supply of air for combustion and/or cooling is insufficient. As will now be further described, exemplary water heater 100 can detect when elevated temperatures are occurring and take precautionary steps.

Once temperature TP reaches or exceeds a predetermined temperature, TP_(MAX), controller 154 can determine that an abnormal condition (e.g., high temperature due to inadequate air flow) exists in combustion chamber 110 such that corrective action should be taken including e.g., terminating the flow of gaseous fuel to burner 108 by closing valve 146. In one exemplary embodiment, TP_(MAX) is 1200° F. In another exemplary embodiment, TP_(MAX) is 1300° F. Other exemplary values for TP_(MAX) indicative of an abnormal condition in combustion chamber 110 may be used as well.

FIG. 6 illustrates a flowchart of an exemplary method 300 of operating water heater 100. Method 300 is provided by way of example, other methods involving different or additional steps may be used as well. During operation, as previously described, thermopile 156 generates a signal representing temperature, TP, in combustion chamber 110. The signal is received by controller 154 of gas control valve module 118. In the event controller 154 determines TP is <TP_(PILOT), then in step 304 controller 154 ascertains that the pilot light 150 is out. Under such condition, controller 154 ensures that valve 146 is closed and that the flow of fuel to pilot burner 148 through line 152 is closed. In such case, the user must manually override gas control valve module 118 to cause gas to flow to pilot burner 148 while causing igniter 158 to spark. In an alternative embodiment, controller 154 determines that TP is <TP_(PILOT) for at least a predetermined period of time, Δt_(PILOT), before ensuring that gaseous fuel is not flowing to pilot burner 148 and burner 108. In one exemplary embodiment, Δt_(PILOT) is 1 second. However, other time periods may be used for Δt_(PILOT) as well.

Alternatively, in the event controller 154 determines TP is ≥TP_(PILOT), then in step 306 controller 154 ascertains that the pilot light 150 is present. Controller 154 then determines if TP is <TP_(MAX). If such condition is met, controller 154 would next determine in step 308 that water heater 100 is operating in a normal condition. For example, either the pilot light 150 is present without a flame 162 at burner 108 or, alternatively, a flame 162 is also present at burner 108. Regardless, because an abnormal temperature condition is not detected, controller 154 does not take evasive action.

However, as indicated in step 310, if controller 154 receives a signal from thermopile 156 indicating TP is ≥TP_(MAX), as depicted in step 310, controller 154 would then determine in step 312 that water heater 100 is operating in an abnormal condition. For example, high temperature combustion may be occurring. In such case, controller 154 would then take corrective action such as terminating the flow of gaseous fuel to burner 108 by closing valve 146. In an alternative embodiment, controller 154 determines that TP is ≥TP_(MAX) for at least a predetermined period of time, Δt_(MAX), before ensuring that gaseous fuel is not flowing to burner 108. In one exemplary embodiment, Δt_(MAX) is 1 second. However, other time periods may be used for Δt_(MAX) (as well.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

1. A gas fueled water heater, comprising: a tank for storage of water for heating; a combustion chamber; a gas burner positioned adjacent to the tank and within the combustion chamber, the gas burner configured for heating the water in the tank; a valve controlling a flow of gaseous fuel to the gas burner; a thermopile positioned within the combustion chamber near the gas burner; the thermopile configured to provide a signal representing temperature, TP, as measured in the combustion chamber; a controller configured for receiving the signal from the thermopile, and terminating a flow of gaseous fuel to the gas burner if the temperature TIP is the same or greater than a predetermined maximum temperature, TP_(MAX).
 2. The gas fueled water heater of claim 1, wherein the predetermined maximum temperature, TP_(MAX), is 1200° F.
 3. The gas fueled water heater of claim 1, wherein the predetermined maximum temperature, TP_(MAX), is 1300° F.
 4. The gas fueled water heater of claim 1, further comprising: a pilot burner for providing a pilot light to ignite the gas burner; wherein the controller is further configured for terminating a flow of gaseous fuel to the pilot burner if the temperature TP is less than a predetermined temperature, TP_(PILOT).
 5. The gas fueled water heater of claim 4, wherein TP_(PILOT) is 500° F.
 6. The gas fueled water heater of claim 4, wherein TP_(PILOT) is 510° F.
 7. The gas fueled water heater of claim 1, wherein the thermopile provides energy to power the controller.
 8. The gas fueled water heater of claim 1, wherein the controller provides a signal to close the valve if the temperature TP is greater than the predetermined maximum temperature, TP_(MAX).
 9. The gas fueled water heater of claim 1, herein the controller provides a signal to close the valve if the temperature TP is greater than the predetermined maximum temperature, TP_(MAX) for at least a predetermined period of time Δt_(MAX).
 10. A method of operating a gas fueled water heater, the water heater having a combustion chamber and a thermopile for measuring temperature in the combustion chamber, the method comprising: generating a signal representing the temperature, TP, in the combustion chamber as measured by the thermopile; and determining whether the temperature TP is the same or greater than a predetermined temperature TP_(MAX) and, if so, then terminating a flow gaseous fuel to a gas burner located in the combustion chamber.
 11. The method of operating a gas fueled water heater as in claim 10, further comprising terminating a flow of gaseous fuel to the gas burner in the combustion chamber if the temperature TP is the same or greater than TP_(MAX) for a predetermined period of time Δt_(MAX).
 12. The method of operating a gas fueled water heater as in claim 10, wherein the terminating a flow of gaseous fuel comprises closing a valve.
 13. The method of operating a gas fueled water heater as in claim 10, wherein TP_(MAX), is 1200° F.
 14. The method of operating a gas fueled water heater as in claim 10, wherein TP_(MAX), is 1300° F.
 15. The method of operating a gas fueled water heater as in claim 10, further comprising ascertaining whether temperature TP is less than a predetermined temperature T_(PPILOT) and, if so, then terminating a flow gaseous fuel to a pilot burner located in the combustion chamber.
 16. The method of operating a gas fueled water heater as in claim 15, wherein TP_(PILOT) is 500° F.
 17. The method of operating a gas fueled water heater as in claim 15, wherein TP_(PILOT) is 505° F. 